The present invention relates to the technology of a loudspeaker system.
Various types of loudspeaker system have been developed, as represented by the use of a bass-reflex or a drone cone, for example.
The bass-reflex reinforces the bass, using a Helmholtz resonance, and the drone cone mounts a loudspeaker unit having no drive circuit, and reinforces the bass, using a resonance with the air within the volume of an enclosure.
In the bass-reflex, in the case where the volume of the enclosure is small, it is required to make a resonant tube smaller and longer to lower the resonant frequency, so that the air resistance is increased to remarkably degrade a bass augmentation function, and the speed of air passing through the resonant tube is very fast, leading to a problem that the wind noise of a flute occurs.
Also, in the drone cone, it is required to increase its mass to lower the resonant frequency. And to lower the resonant frequency, it is required to increase the compliance of the edge supporting the diaphragm, but to support the diaphragm of large mass, it is required to increase the spring property or strength of the edge, which is reciprocal to the compliance. Also, it is difficult that the heavy diaphragm is vibrated completely parallel, often attended with an abnormal vibration called a rolling or rocking. This abnormal vibration increases distortion and decreases the efficiency by consuming energy uselessly.
To compensate for a shortcoming of the drone cone, a method was offered in patent document 1, for example. With this method, the rolling or rocking can be prevented, but due to a structure that the weight of the diaphragm (flap) is borne by the edge provided peripherally, the edge is required to have strength, leading to a problem that Q of the vibration is smaller because of its damping effect.    [Patent document 1] WO00/32010